This invention relates to patient monitoring systems and more particularly to patient monitoring systems in which the movement or location of a patient is determined by any of a plurality of redundant or cooperating sensors and when one or more of the sensors indicates a problem with the patient provides an alarm or a warning.
In one class of patient monitoring systems, a sensor indicates the departure of a patient from his or her expected position and the system responds by providing an alarm. In one such system, a fastener is connected to a monitoring housing by a cord or other device having a fixed length so that if the fastener moves beyond that length, the monitoring housing is activated. The fastener is connected to a patient such as to the clothing of a patient by a clip so that, if the patient moves beyond a fixed distance such as by slumping from a wheelchair onto the floor or moving from a bed, the monitoring housing provides an alarm.
In a prior art monitoring system of this type, the end of the cord opposite to the fastener is loosely fitted into the monitoring housing so that, when the patient moves away from the monitoring housing a distance greater than the length of the cord, that end is pulled free. When the end is pulled free from the monitoring housing, an alarm is given. Prior art systems of this type are disclosed in U.S. Pat. Nos. 4,577,185, 4,858,622, and 4,583,084 and systems of this type are on sale under the trademark, TABS, by Wanderguard, Inc., a division of Senior Technologies, Inc., located at 1620 North 20th Street, P.O. Box 80238, Lincoln, Nebr. 68503.
This type of prior art patient monitoring system has several disadvantages, such as for example: (1) from time to time the fastener falls loose from the patient or is removed by the patient so that the system fails; (2) the patient may become entangled in bedding or the like or fall from the bed or chair or partly fall at a distance that does not pull the cord free; and (3) the cord may break or be cut.
In another class of patient monitoring systems, the patient in a bed or a wheelchair rests on or near a pressure pad. Changes in pressure on that pad cause a signal indicating that the patient is moving in a manner that indicates some type of problem. In a prior art monitoring system of this type, a manual switch is activiated by an attendant or patient when the patient is in place to initiate the monitoring system and inactivated when the patient leaves in an ordinary untroublesome manner. One such prior art system is disclosed in U.S. Pat. No. 4,907,845.
This type of prior art monitoring system has several disadvantages such as for example: (1) the switch may be accidentially thrown or thrown by a patient intending to move but for whom it is undesireable to move unattended because of confusion of the patient or illness to the extent that the patient does not appreciate; (2) because the pressure pad is positioned in the bed beneath the patient, it flexes as the patient moves, causing the cord to flex, eventually fail and thus prevent the signal being given if the patient leaves; and (3) the pad may be defeated by folding or placing a weight on it.